The sol-gel method is well known from the prior art, simple to implement, takes place under mild conditions and facilitates the shaping of materials (Brinker and Scherer, 1990). In standard fashion the sol-gel method consists of a hydrolysis and condensation method which, starting from a molecular precursor (true solution) leads to the formation of a colloidal solution (or sol) then, by connection of the colloidal particles, to the formation of a continuous solid skeleton named a gel. The non-hydrolytic sol-gel method is a particular case of the sol-gel method, taking place in the absence of water (Vioux, 1997). Another notable particular case consists of a sol-gel method for obtaining silica gels by using formic acid (formation of water in situ) (Sharp, 1994; Dai, 2000).
Ionic liquids are formed by the combination of cations and anions and are in the liquid state at temperatures close to ambient temperature. They have remarkable properties such as zero volatility, a high ionic conductivity as well as catalytic properties. They are currently used in numerous fields, in particular as electrolytes (Bonhôte et al., 1996; Olivier-Bourbigou et al., 2000; Branco et al., 2002; Doyle et al., 2000; Noda et al., 2000; Sun et al., 2001; Aurbach et al., 2008 Journal of Power Sources, DOI:10.1016/j.jpowsour.2008.09.099).
International patent application WO 2005/007746 describes ionogels which are ionic conductors presented in the form of a monolithic solid in which an ionic liquid is confined in order to combine the physico-chemical properties of a mineral or organomineral solid with those of an ionic liquid. These ionogels are produced in a single step which consists of mixing in homogeneous phase a solution, in ionic liquid medium, of one or more sol-gel precursors (alkoxysilane, alkylalkoxysilane, arylalkoxysilane, halogenosilane, halogenoalkoxysilane, metal alkoxide, metal alkylalkoxide or metal arylalkoxide, metal halide, etc.), alone, or in the presence of an aqueous solution (acid, basic, saline, etc.), of a carboxylic acid, or another oxygen donor (alcohol, ether, etc.).
Although these ionogels have many useful properties, their use as electrolytes also has drawbacks due to their high propensity to shrink during preparation, a low solidity leading to an electronic short circuit between the two electrodes that the ionogel must separate, and to a water content that is too high for use with lithium.
Solid batteries are batteries where the electrodes and the electrolyte are solids; the electrolyte being an insulating compound which electronically separates the positive electrode from the negative electrode while allowing the passage of ionic species (Li+, Na+ or Mg 2+ ions) between the two. Such batteries make it possible to reduce the risks of leakage of liquids, calcination, emission of gasses etc. that are observed with batteries using conventional liquid electrolytic solutions and as a result the safety of use is improved. However, due to the relatively low conductivity of the solid electrodes and electrolytes, the batteries obtained are produced in thin layers, and as a result deliver a low energy density per unit of surface area.